1. Field of the Invention
The field of art to which the present invention pertains is the processing of protein from soybeans. In conventional practice, soy grits are extracted in an effort to maximize the total yield of protein and minimize undesirable properties as, for example, color, odor and off-taste. An excellent in-depth discussion of soybean processing techniques is found in a book entitled Soybeans: Chemistry and Technology, Smith and Circle, Volume I ("Proteins"), The AVI Publishing Company, Inc., Westport, Connecticut, 1972. This book will be referenced hereafter as the "Smith and Circle work".
At page 319 of the Smith and Circle work appears a discussion relating to the processing of soy protein isolate that delineates an appropriate background for the present invention. The source material discussed is defatted soy meal or flour of a high nitrogen solubility index ("NSI"). Included also is a schematic of a typical process flow, and descriptions of aqueous extraction, clarification, precipitation, cured-whey separation and drying. The discussion concludes at page 323 with a brief description of the problems of complete economic recovery of whey solubles with a statement that, "If these problems could be solved, properly processed soy solubles would readily find a place in foods or animal feeds, or could be used as a source material for further fractionation" The present invention is directed to a solution of these problems of economic recovery of whey solubles and the provision of source material for fractionation as alluded to in the Smith and Circle work, and the present invention further is directed to the provision of novel and useful protein fractions having such unique physical or functional characteristics that they are highly useful in various food products.
2. Prior Art Statement.
Applicants are aware of United States patents having relevant disclosures relating to the recovery of protein from soybeans, four of the most relevant being U.S. Pat. Nos. 2,451,659, 2,479,481, 3,303,182 and 3,607,860. U.S. Pat. No. 2,451,659 sets forth in Example I what purports to be "a typical standard process for isolating soybean protein." The process described includes aqueous extraction (with sodium hydroxide added) of substantially oil-free soybean flakes at a temperature of 45.degree. C. followed by clarification and then acidification to precipitate the protein. The precipitated protein curd is then air-dried at 45.degree. C. In contrast, conditions according to the present invention vary substantially from the "typical standard process" thereby enabling successive fractionation steps for recovery of unique protein compositions. The other three patents likewise disclose various techniques for the production of soybean protein, none of which teaches the extraction or fractionation techniques according to the present invention.
Applicants are also aware of published literature including an article by Wolf and Briggs entitled "Purification and Characterization of the 11S Component of Soybean Proteins," Archives of Biochemistry and Biophysics, Volume 85, pages 186-199 (1959); an article by Briggs and Mann entitled "An Electrophoretic Analysis of Soybean Protein," Cereal Chemistry, Volume 27, No. 3, pages 243-257 (1950); an article by Eldridge and Wolf, entitled "Purification of the 11S Component of Soybean Protein," Cereal Chemistry, Volume 44, pages 645-651 (1967); an article by Wolf and Sly, entitled "Cryoprecipitation of Soybean 11S Protein," Cereal Chemistry, Volume 44, pages 653-668 (1967); and an article by Smith, Circle and Brother entitled "Peptization of Soybean Proteins. The Effect of Neutral Salt of the Quantity of Nitrogenous Constituents Extracted from Oil-Free Meal," Journal of the American Chemical Society, Volume 60, pages 1316-20 (1938). Each of these articles is relevant in the sense of discussing the various extraction procedures for recovery of soybean protein or low temperature precipitation of defatted soybean meal. However, none teaches the extraction procedures according to the present invention or the fractionation techniques resulting in the unique protein compositions as described and claimed herein.
Finally, the Smith and Circle work is relevant in virtually its entirety although the discussions at pages 101 and 319-324 are most pertinent. As stated previously, however, Smith and Circle merely allude to the problem for which the present invention effectively provides a solution.